Conventionally, a Ni-plated steel sheet has been popularly used for manufacturing a battery can.
Also, to further enhance the corrosion resistance of a Ni-plated steel sheet, after Ni plating, Ni is diffused in the steel sheet by heat treatment.
For example, patent document 1 (JP-A-61-235594) discloses a Ni-plated steel sheet where Ni plating is applied to a steel sheet at an adhesion amount of 9 to 62 g/m2 for one-side surface before diffusion by heating and, thereafter, heat treatment is applied to the steel sheet thus forming an Fe−Ni alloy layer having a thickness of 4 μm or less on the steel sheet, and a method of manufacturing such a Ni-plated steel sheet.
Further, patent documents 2 (Japanese Patent 3045612) discloses an Ni-plated steel sheet used for manufacturing a battery can where a Ni-plating layer is formed on a cold-rolled steel sheet and, thereafter, thermal diffusion treatment is applied to the steel sheet thus turning the Ni-plating layer into an Fe−Ni diffusion layer.